Contact has been lost with Mars Probe 7. When contact is also lost with the recovery ship, UNIT is called in and the Doctor learns that someone is sending messages to the vessel.
| Name | Type | Role | |
|---|---|---|---|
| David Whitaker | Writer | ||
| Trevor Roy | Writer | ||
| Robert Robertson | Guest Star | ||
| Ray Armstrong | Guest Star | ||
| Cheryl Molineaux | Guest Star | ||
| Robert Cawdron | Guest Star | ||
| Michael Ferguson | Director |